Popping a couple zinc supplements at the start of cold could save about two days of sniffling, at least for adults, finds a new review.

A analysis of 17 studies involving 2,121 people aged 1 to 65 found that taking zinc either as a lozenge, pill or syrup helped adults kick their cold symptoms more than two days sooner than adults who did not take zinc. However, zinc didn’t lessen the severity of their cold symptoms.

Also, for kids, zinc had little to no effect, a result that could be due to the type of zinc used by kids or because there wasn’t enough data on children overall, the authors said.

In the studies, the participants were randomly assigned to take zinc or a placebo within three days of contracting a cold. The researchers found that for adults, higher doses of zinc worked best, but the treatment came at a price. Side effects were common: zinc-takers were 64% more likely to have nausea and 65% more likely to have an unpleasant taste, compared with those taking placebo.

“Although oral zinc can impact the duration of [the] common in adults, there is not enough evidence to recommend its use in children, and only a weak rationale for its use in adults,” lead researcher Dr. Michelle Science, an infectious disease specialist at the Hospital for Sick Children in Toronto, told WebMD.

The research team notes that their conclusions are based on studies that varied widely in terms of methods and doses used. The studies also did not look at zinc nasal sprays, which have been linked to loss of smell, or at using both zinc and vitamins.

Zinc researcher Dr. Ananda Prasad, a professor of medicine at Wayne State University in Detroit, Michigan, who was unaffiliated with the study, told WebMD that he didn’t agree with the findings because many of the zinc formulations in the review were likely inactive. WebMD reported:

“The chemistry is important,” he says. “The chemical composition has to be right so zinc is released, and it must be started within 24 hours of cold onset to be effective.”

He suggests only choosing zinc acetate or zinc gluconate lozenges.

The researchers recommend that cold sufferers consult with their physicians before trying supplements.